<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var person={
            age:18,
            sex:'boy',
        };
        // person.hobby='eat';
        // person.sex='girl';
        // delete person.age;
        // console.log(person.age);
        person['hobby']='eat';
        console.log(person['sex']);
    </script>
</body>
</html>